Endoscopic needle stylet with enhanced-flexibility lengths

ABSTRACT

A single-wire stylet may be constructed as an elongate single-wire, memory-metal alloy body with a generally cylindrical body profile, extending distally from a proximal end terminus, where embodiments include a polymeric distal tip member fixedly attached directly at a distal end of the single-wire body. At least one lengthwise portion of the single-wire body is at least partially in martensitic phase at operating temperatures at and below about 37° C. Where present, the polymeric distal tip member has a generally cylindrical body profile circumferentially bounded by an outer circumference substantially equal to or greater than that of the metal body. The polymeric distal tip member may be overmolded upon a distal-end tip length of an elongate single-wire, memory-metal alloy stylet body, where the distal end and/or discrete intermediate distal-portion length(s) that include martensitic-phase alloy and any polymeric member have greater flexibility than a proximal-most length of the alloy stylet body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims priorityto U.S. provisional application Ser. No. 62/161,577, filed May 14, 2015,which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

Embodiments disclosed herein generally relate to medical deviceappliances. More particularly embodiments disclosed herein relate tostylets used within the lumen of endoscopic ultrasound needles duringendoscopic ultrasound (EUS) procedures.

BACKGROUND

Endoscopic ultrasound (EUS) procedures including endobronchialultrasound (EBUS) procedures, as well as other endoscopy procedures(e.g., endoscopic retrograde cholangiopancreatography (ERCP) techniquesused for viewing and treating the ducts that drain the liver andpancreas) provide advantageous, minimally-invasive means for diagnosisand treatment of many conditions. The body structures and passages thatmust be navigated with the scope-based devices present challenges forminimizing procedure times while maximizing efficacy of diagnosticand/or therapeutic procedures.

For example, with reference to gastrointestinal procedures, biliaryducts form a drainage routes into the duodenum from the liver andgallbladder and they join the pancreatic duct, just before they draininto the duodenum about 3 inches from the stomach. The drainage openingis called the papilla (Ampulla of Vater). The papilla is surrounded by acircular muscle, called the sphincter of Oddi. During ERCP, X-raycontrast dye may be injected into the bile duct, the pancreatic duct, orboth via a catheter disposed through a working channel of an endoscopeto aid fluoroscopic visualization of procedures. Those same systems maybe accessed and visualized using EUS procedures, where use of ultrasoundhelps to reduce the amount of fluoroscopy exposure time spent by apatient and treating personnel.

A broad variety of techniques using ERCP and EUS (including in thegastrointestinal tract and elsewhere in patient bodies) have been andcontinue to be developed for minimally-invasive diagnosis and treatmentof various conditions in a patient's gastrointestinal tract, andparticularly in the structures of the biliary and pancreatic systemsbranching off from the duodenum. For a number of procedures using smallgauge needles (often 19 ga. or smaller), the needle is introduced with astylet disposed through the entire length or nearly the entire length ofits longitudinal needle lumen. A standard bevel-tipped stylet 174 isshown in FIG. 1, including a proximal end cap 176 and a flexibleelongate body 178. The stylet provides columnar strength while theneedle is being directed to a target site, as well as minimizing thelikelihood that an open distal tip and/or side aperture of, for example,a biopsy needle will collect tissue en route to the actual site beingtargeted.

In a biopsy procedure, the stylet will be removed from (or at leastpartially longitudinally retracted within) the needle lumen, typicallyafter the needle is directed through an endoscope working channel sothat its distal end is in or near the target site. As shown in FIG. 2,the endoscope (illustrated here as a duodenoscope 181, but readilyunderstandable with application to an EUS scope) is directed down apatient's esophagus 191, then through the body, and up and around thepylorus of the stomach 193, then down/around into the duodenum 195. Forthe side-viewing camera and ports to properly orient relative to thesphincter of Oddi 197 and access the primary and branchingducts/passages of the biliary tree 199, the distal end portion of theendoscope 181 may be flexed/bent 90 degrees or more relative tolongitudinal axis of the scope and to the already-curved scope bodyportion situated through the pylorus and duodenum, which is also shown.As such, the coaxial arrangement of a stylet within a biopsy needleassembly, oriented through an endoscope working channel is placedthrough a series of curves and turns between the proximal end accessedby an endoscopist and other treating personnel and the distal end (e.g.,accessing the biliary tree), along and through all three axes of thepatient's body.

It will be appreciated that this presents a relatively tortuous path fora needle disposed through the length of the endoscope 181. The samewould be true for an EUS procedure, whether access is gained through acannulated sphincter or by traversing a wall of the stomach, duodenum,or other structure. Thus, a stylet occupying the needle lumen mayrequire significant force for withdrawal and removal (e.g., about 50 toabout 100 Newtons), due to the binding friction between the outersurface of the stylet and the inner needle lumen surface along theirrespective lengths—and particularly along lengths where the scope istwisted and/or tightly curved. Stated differently, those of skill in theart will appreciate that certain points or lengths along the path of astylet through a needle lumen may present greater frictionalcontact/binding force due to curvature of the needle (both on its ownand relative to/interacting with an accessory channel of an endoscopethrough which it is disposed), causing an increased removal forcerequired to remove the stylet from the needle lumen, as compared to aless curved, twisted, or otherwise distorted path. This higher level ofremoval force is inconvenient to the users, and it may have a negativeimpact on efficient workflow (e.g., by increasing the likelihood thatthe needle and/or scope is moved out of the desired position and/ororientation during stylet removal, by increasing procedure time, orother factors).

It may be desirable to provide a stylet and a stylet-needle systemincluding a stylet structure that provides for reduced removal forcewithout diminishing its other stylet functionality.

BRIEF SUMMARY

In one aspect, embodiments disclosed herein include a single-wire styletincluding a proximal end terminus and a distal end terminus, constructedas an elongate single-wire, memory-metal alloy body with a generallycylindrical body profile that is circumferentially bounded by a firstouter circumference, extending distally from the proximal end terminus,where embodiments include a polymeric distal tip member fixedly attacheddirectly at a distal end of the single-wire body. At least a lengthwiseportion of the single-wire body is at least partially in martensiticphase at operating temperatures at and below about 37° C. Where present,the polymeric distal tip member has a generally cylindrical body profilecircumferentially bounded by a second outer circumference that issubstantially equal to or greater than the first outer circumference.

In one aspect, stylet embodiments disclosed herein may include apolymeric distal tip member overmolded upon a distal-end tip length ofan elongate single-wire, memory-metal alloy stylet body, where thedistal end and/or discrete intermediate distal portion length(s) havegreater flexibility than a proximal-most length of the stylet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a standard prior art stylet;

FIG. 2 shows an endoscope deployed in a patient body, indicating thesinuous, tortuous, and/or constricted path that a needle and stylet mayneed to follow (e.g., to access the head of a patient pancreas);

FIGS. 3A-3C show stylet embodiments with a generally consistent outercircumference along the stylet body length; and

FIGS. 4A-4C show stylet embodiments with a generally consistent outercircumference along a metal stylet body length with a larger outercircumference along a distalmost polymeric tip body length.

DETAILED DESCRIPTION

Various embodiments are described below with reference to the drawingsin which like elements generally are referred to by like numerals. Therelationship and functioning of the various elements of the embodimentsmay better be understood by reference to the following detaileddescription. However, embodiments are not limited to those illustratedin the drawings. It should be understood that the drawings are notnecessarily to scale, and in certain instances details may have beenomitted that are not necessary for an understanding of embodimentsdisclosed herein, such as—for example—conventional fabrication andassembly, as well as showing highly flexible structures (e.g., styletsand/or needles) only in a generally straight line, when those of skillin the art will appreciate that they can be highly flexible fornavigation through tortuous passages.

A stylet for within an endoscopy needle is described, including featuresthat provide reduced removal force as compared to a standard stainlesssteel, nitinol, or other standard stylet. The phrase “within anendoscopy/endoscopic needle” should be understood as meaning that all orsubstantially all of the stylet length fits within and, when in usewill, at some time, be disposed within the lumen of a needle, includingthat the distal end terminus of the stylet will not extend beyond thedistal needle end terminus. The phrase “substantially within anendoscopy/endoscopic needle” should be understood as meaning thatsubstantially all of the stylet length fits within and, when in usewill, at some time, be disposed within the lumen of a needle, includingthat the distal end terminus of the stylet will not extend substantiallybeyond the distal needle end terminus (e.g., in certain embodiments, astylet may extend up to a few—that is most likely fewer than about 10,and highly likely fewer than 5—millimeters beyond a surrounding needle'sdistal end terminus). The reduced removal force may be provided byenhanced flexibility along at least a length of a metallic stylet bodyportion (e.g., by constructing it of a memory metal material thatmaintains some or all martensitic phase at operating temperaturesbetween about 20° C. to about 40° C., and at least at or below theoperating temperature of a patient's body such as 37° C.) and providinga more flexible, lower friction polymeric distal tip member along ordefining a distalmost length of the stylet body, as is described below.

Methods of making a stylet may include specific heat-treatment of one ormore lengths of a memory metal wire (e.g., a nickel titanium or othermemory metal alloy) to provide desired flexibility. In particular, it isdesirable that up to about 30% of the distal length of a stylet behighly flexible so as to minimize retraction force. In some embodiments,up to 70%, or even up to 100% of the stylet body length may beconfigured for increased flexibility (i.e., as compared to a standardmetal alloy needle stylet of the same length and configured for usewithin the same needle gauge). A method has been devised to fabricate ahybrid stylet comprising a memory metal alloy that can exhibit twodifferent flexibility behaviors at temperature ranges including bodytemperature (37° C.). The technology devised enables the creation of asingle-wire stylet, the metallic length of which is free from any jointsor welds. The hybrid stylet, which may be made from a single continuouswire, can be used for endoscopic and other applications where a needle(e.g., a biopsy needle or access needle) occupied by the stylet mayprovide points and/or lengths of constriction that increase retractionforce.

The method includes controlling the austenite transformationtemperatures (A_(s), A_(f)=austenite start, austenite finishtemperatures) of a shape memory alloy such as Nitinol in differentportions of a stylet. When A_(s) and A_(f) have values below bodytemperature, the shape memory alloy is fully austenitic at bodytemperature and superelastic deployment of a pre-formed shape ispossible. However, when A_(s) and A_(f) have values above bodytemperature, the memory metal alloy remains martensitic at bodytemperature and plastic deformation remains readily usable/available,which provides for the desired flexibility or malleability of thepresent stylet design. As such, at least a lengthwise portion of thesingle-wire body of stylet embodiments described herein preferablyremains in martensitic phase at operating temperatures between about 20°C. to about 40° C., and most preferably remains in martensitic phase atoperating temperatures of body temperature plus the standard variationsof temperature likely in an operating environment (e.g., for a humanpatient, about 37° C., plus up to about 10° C.). Those of skill in theart will appreciate that lower operating temperatures are unlikely toeffect a phase change that would decrease flexibility of a martensiticshape memory wire length.

The invention is defined by the claims, may be embodied in manydifferent forms, and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey enabling disclosure to those skilled in the art. As used in thisspecification and the claims, the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.

The terms “proximal” and “distal” are used and defined herein in thecommon usage sense where they refer respectively to a handle/doctor-endof a device or related object and a tool/patient-end of a device orrelated object. The term “stylet” as used herein is should be understoodas different that guidewire structures that are used through, andextending well beyond the distal end of, endoscopic and otherminimally-invasive needles, where a stylet of the present disclosure isa single-wire device that expressly excludes an overlying coil wire, andthat does not include other distal tip features configured forsteerability in the manner of guidewires. The term “about” when usedwith reference to any dimension, proportion, or other quantitative valueis intended to communicate a definite and identifiable value within thestandard parameters that would be understood by one of skill in the art(a medical device engineer with significant experience in the field ofminimally invasive endoscopy needles and devices), and should beinterpreted to include at least any legal equivalents, minor butfunctionally-insignificant variants, and including at leastmathematically significant figures. The relative definitions offlexibility (e.g., “more flexible” and “less flexible” with reference toa stylet) will readily be understood by those of skill in the art asused herein; specifically, a “more flexible” length will be coilable andbendable around smaller/tighter radii of curvature than will a “lessflexible” length—without imposing a crimp, bend, fold or other permanentdistortion.

One embodiment of a stylet for use within an endoscopy needle isdescribed with reference to FIG. 3A, which shows asimplified/diagrammatic side view of a first stylet embodiment 100. Thestylet 100 includes an elongate single-wire, memory-metal alloy body 102with a generally cylindrical body profile that is circumferentiallybounded by a first outer circumference. For example, the transversecross-section of the body 102 may be circular or at least generallycircular (that is, allowing for manufacturing tolerances and includingnear-circular geometric shapes). A polymeric distal tip member 106 isfixedly attached directly at a distal end of the single-wire body 102.The polymeric distal tip member 106 has the same generally cylindricalbody profile as the single-wire body 102, and it is circumferentiallybounded by a second outer circumference that is equal or substantiallyequal to the first outer circumference. By “substantially equal,” thoseof skill in the art will understand that the outer circumferences aregenerally the same within normal manufacturing tolerances and variancesdue to slight relative contraction or expansion upon heating, cooling,and during use. The polymeric distal tip member 106 is shown with abeveled distal terminal end tip.

The polymeric distal tip member of this and other embodiments mayinclude or consist of any biocompatible polymer suitable for forminginto the structure described. In certain embodiments, the polymericdistal tip member may be constructed of a polymer selected from apolyetheretherketone (PEEK), polycarbonate, polytetrafluoroethylene(PTFE), silicone, latex rubber, non-latex rubber, thermoplastic polymers(including, e.g., PEBAX), and any combination thereof. The externalsurface of the polymeric distal tip member preferably is lubricious orotherwise configured to present a low efficient of friction when used inthe lumen of a needle (where the inner circumference of the needle isabout the same as or only slightly greater than the outer circumferenceof the polymeric distal tip member, as is well-known and characterizedfor relative proportions of stylets and coaxially-overlying needles).The fixed attachment of the polymeric distal tip member to thesingle-wire body may be effected by one or more of overmolding,adhesive, epoxy, friction-fit interface, or any combination thereof, aswell as other means known or developed in the art for attaching theparticular selected construction materials.

Different stylet embodiments may have different lengths. For example, astylet configured for use in an endobronchial ultrasound needle may beabout 1 meter in length, while a stylet configured for use in agastrointestinal endoscopic ultrasound needle (e.g., for accessing andbiopsying the head of a human pancreas may be about 1.7 meters inlength. Preferably, at least about one-tenth, and more preferably atleast about one-fourth of the distal length to about one-half of thedistal length of the single-wire metal alloy body is in martensiticphase at operating temperatures (e.g., patient body temperature for ahuman or non-human patient). For a stylet single-wire body in which lessthan the entire length is in martensitic phase at operatingtemperatures, the other (non-martensitic phase length) may undergo athermal process different than the distal martensitic phase length, asset forth below.

To fabricate a hybrid stylet single-wire body that has a distallengthwise portion with different martensitic/austenitic stateproperties that a proximal lengthwise portion of the wire, the differentportions will undergo different thermal processing treatments. As aresult, different austenite transformation temperatures are achieved ineach portion of the wire. The specific heating time and temperature foreach length will be determined by the specific memory metal alloyselected, as is known in the art. Typically, heat setting is carried outat a temperature between about 350° C. and about 550° C. for a timeduration of about 5-180 min. For the present embodiments, the length ofsingle-wire body that is to remain in a martensitic phase at operatingtemperature within a patient body, the time and temperature ofheat-treatment are likely to be near the upper ends of those ranges,depending upon the specific memory metal alloy selected. Most preferablyboth the austenite start (A_(s)) and the austenite finish (A_(f))temperatures will be above the operating temperature within a patientbody, e.g., greater than about 37° C., where certain embodimentspreferably will maintain the desired lengthwise portion of thesingle-wire body in martensitic phase at operating temperatures up toabout 40° C. or greater. The heat treatment may be isolated to a desiredlength of a continuous piece of wire using means known in the art,including passing current along the wire between selected contact pointsdefining the length being treated. The non-heat-treated proximal length,if any, may be protected from transformation by means known in the art(e.g., exposure to cooling fluid during the heat treatment of the otherlength(s)).

Depending upon the specific memory metal alloy selected, the wire asdrawn may have desirable flexibility/malleability properties for aproximal length. As such, the proximal length may be treated in a mannerproviding A_(s) and/or A_(f) temperatures that are at or below theaforementioned operating temperatures. In this manner, the proximallength may be more rigid than the treated/martensitic phase distallength (although still retaining desirable flexibility for use in themanner of known stylets). The change in the austenite transformationtemperatures in the distal portion of the single-wire body as aconsequence of the heating (e.g., in a sand bath, by use of current, orother means) may be understood in view of microstructural changes thatoccur. For example, when the shape memory alloy is an equiatomic ornear-equiatomic nickel-titanium (Ni—Ti) alloy, the temperature increasemay cause nickel-rich precipitates to form in the alloy, producinglocalized shifts in composition and depleting the Ni—Ti alloy matrix ofnickel.

However, the overall composition of the alloy remains the same. Due tothe localized depletion of nickel from the Ni—Ti alloy matrix, theaustenite transformation temperatures (A_(s) and A_(f)) may increase.When heated for sufficient time, the A_(s) temperature of the distalportion of the single-wire body increases above 37° C., ensuring thatthe Ni—Ti alloy remains martensitic at body temperature. Thus, thedistal portion of the stylet body most likely to encounter binding,constriction, and/or tortuous passages that would increase retractionforce. Because only the distal portion of the single-wire stylet bodyexperiences the heat treatment (e.g., due to the selected method ofheating, optionally complemented by cooling of the proximal portion),the initial austenite transformation temperatures in the proximalportion do not change substantially. Accordingly, the proximal portionof the stylet remains flexible and may be superelastic at bodytemperature. The foregoing methods may be used in preparing thesingle-wire body for each of the embodiments described herein.

It should also be appreciated that this disclosure provides for a styletembodiment not including a polymer distal tip member, but just asingle-wire body. In such an embodiment, a distalmost length of the wireis malleable and more highly flexible than a proximal-most length,because the distalmost length is prepared and maintained in at least apartially martensitic phase up to and/or above a patient's bodytemperature (e.g., 37° C., and as described elsewhere herein), providingfor the desirable performance features described with reference to theother embodiments of this disclosure. Such an embodiment may have ageneral external appearance similar or even identical to the stylet ofFIG. 1, but will have the novel flexibility differences based upon themartensitic properties of selected and identified length(s) of thesingle-wire body.

Another embodiment of a stylet for use within an endoscopy needle isdescribed with reference to FIG. 3B, which shows asimplified/diagrammatic partial-longitudinal-section view of a secondstylet embodiment 200. The stylet 200 includes an elongate single-wire,memory-metal alloy body 202 with a generally cylindrical body profilethat is circumferentially bounded by a first outer circumference. Forexample, the transverse cross-section of the body 202 may be circular orat least generally circular, although non-circular transverse sectionbodies may be considered as cylindrical within the scope of the presentapplication. A polymeric distal tip member 206 is fixedly attacheddirectly at a distal end of the single-wire body 202. The polymericdistal tip member 206 has the same generally cylindrical body profile asthe single-wire body 202, and it is circumferentially bounded by asecond outer circumference that is equal or substantially equal to thefirst outer circumference. The joint 205 of the polymeric distal tipmember 206 with the single-wire body 202 may be secured by epoxy,adhesive, or any other appropriate means known or developed in the art.The distal end terminus of the polymeric distal tip member 206 is shownas having a blunt flat end, although this embodiment and all others mayhave any number of end-terminal shapes, including by way of non-limitingexample, hemispherical or otherwise rounded, flat, beveled, conical, orotherwise singly or multiply pointed, or convex.

Another embodiment of a stylet for use within an endoscopy needle isdescribed with reference to FIG. 3C, which shows asimplified/diagrammatic longitudinal section view of a third styletembodiment 300. The stylet 300 includes an elongate single-wire,memory-metal alloy body 302 with a generally cylindrical body profilethat is circumferentially bounded by a first outer circumference. Apolymeric distal tip member 306 is fixedly and directly attached bybeing overmolded (or otherwise permanently/fixedly attached) around adistalmost end length 304 of the single-wire body 302. The polymericdistal tip member 306 has the same generally cylindrical body profile asthe single-wire body 302, and it is circumferentially bounded by asecond outer circumference that is equal or substantially equal to thefirst outer circumference.

Most of the distalmost end length 304 has a third outer circumferenceless than the first and second outer circumferences, and it is shownwith an enlarged portion 304 a that may help secure the polymeric distaltip member 306 alone or along with other fastening means (such as, forexample, epoxy, adhesive, etc.). The enlarged portion 304 a is shown ashaving frustoconical geometry, but those of skill in the art willappreciate that other shapes can be provided to assist inter-engagementof the distalmost end length 304 with the polymeric distal tip member306. In other embodiments (not shown), the distalmost end length 304 maybe tapered, include a wavy, crenellated, serrated, or other surfacegeometry that provides at least lengthwise portion including the thirdouter circumference less than the first and second outer circumferences.The distalmost end length 304 of the single-wire body 302 preferablyoccupies one-half or less of the longitudinal length of the polymericdistal tip member 306. For example, in this and other embodiments athird outer circumference may be about 65% to about 95% of the secondouter circumference. As such, the unoccupied distal-most length of thepolymeric distal tip member 306 preferably will be even more flexiblethan the martensitic phase contacting/immediately-adjacent length of thesingle-wire body 302, which will further provide for decreasinglikelihood of binding/increased retraction force attributable to styletstiffness through certain lengths of a needle lumen (or other lumen)during use.

For each of the embodiments of FIGS. 3A-3C, the first and second outercircumference will be approximately the same as or only slightly lessthan the inner circumference of a needle in and through which eachstylet embodiment will operate and be disposed.

As such, for use in a needle system, the absolute dimensions of thestylet body with its polymeric distal tip member will be determined bythe needle selected. For example, a 19-gauge needle including a centrallongitudinal needle lumen that is 170 cm long preferably will receiveand contain for use during endoscopic introduction a stylet embodimenthaving an outer circumference about the same as or only very slightlyless than the inner needle circumference (understood by those of skillin the art to have about the same respective outer diameter and innerdiameter for a needle and stylet with circular transversecross-sections). The combined length of the single-wire body and itspolymeric distal tip member for such a needle will be about 170 cm. Thepolymeric distal tip member may comprise at least about 5% of the totalstylet length, and in some bodies may comprise up to about 10%, about15%, or even about 20% thereof. The distal portion of the needlecomprising the enhanced flexibility of the martensitic portion of memorymetal single-wire body and polymeric distal tip member most preferablyincludes sufficient length to account for the length of the stylet thatis most likely to encounter the constricted path and/or binding regionsor points when deployed within a needle through an accessory/workingchannel of an endoscope. In the case of a gastrointestinal endoscope, adistal length of these more-flexible portions may include up to aboutone-half of the stylet length. In most embodiments, at least aboutone-tenth up to about one-third of the stylet's distalmost length willaccount for those regions where the enhanced flexibility will provideadvantage over prior art stylets.

In one example, a 19-gauge, 1.7 m biopsy needle is provided including atissue-collection side aperture disposed within a distalmost 10-12 mmlength of the needle body. A stylet according to any embodiment hereindescribed (including variants that combine or exchange features ofseparately described embodiments) is provided through the needle lumen,occupying the entire length thereof without extending substantially pastthe distal terminal needle tip. The polymeric distal tip member occupiesall or very nearly all the cross-sectional needle lumen area for atleast the distalmost needle lumen length through and including the sideaperture, such that the polymeric distal tip member completelycovers/obscures the side aperture when the stylet is fully engaged intothe needle lumen. The more-flexible stylet length including themartensitic phase-containing single-wire stylet body length extendsalong at least 15%-20% of the entire stylet body length, where theremaining proximal length may be in the form/phase as drawn or may be inan austenitic phase. One exemplary needle construction with which thepresent stylet embodiments may be useful is described in U.S. Pat. Publ.No. 2012/0253228 to Schembre, et al., which is incorporated herein byreference. It should also be appreciated that an intermediate and/orproximal length of a single-wire stylet body of the present disclosure(that is a length proximal of a “martensitic at/below body temperature”wire body length) may be configured with a shapeset memory promotingand/or imposing self-coiling behavior in the manner disclosed in U.S.Pat. App. Pub. No. 2014/0114254 to Irwin, et al., which is incorporatedherein by reference.

In one example of an embodiment, a 22-gauge biopsy needle that is 1.7 min length, may be provided for fine needle aspiration or fine needlebiopsy (e.g., with a gastrointestinal EUS endoscope). A stylet accordingto any embodiment herein described (including variants that combine orexchange features of separately described embodiments) may be providedin and through the needle lumen, occupying the entire length thereofwithout extending substantially past the distal terminal needle tip. Themetallic and/or polymeric distal tip member will occupy all or verynearly all the cross-sectional needle lumen area for at least thedistalmost needle lumen length. The more-flexible stylet lengthincluding the polymeric tip and/or martensitic phase-containingsingle-wire stylet body length extends along at least 15%-20% of theentire stylet body length, where the remaining proximal length may be inthe form/phase as drawn or may be in an austenitic phase. In anotherembodiment, a 22-gauge biopsy needle may be provided with a lengthappropriate for use in an endobronchial ultrasound (EBUS) endoscope,and—prospectively—with a different distal-end biopsy-collectionstructure than in the 1.7 m embodiment. Those of skill in the art willappreciate that many EUS and EBUS needles are generally the same intheir design characteristics. The main differences are in the overalllength and needle gauge (Needle OD), as well as the particular tip shapethat may be chosen for biopsy or other purposes. As such, those skilledin the art will appreciate that additional examples of styletembodiments of the present disclosure will be very similar in design tothose expressly disclosed here and may be constructed as informed by thepresent disclosure without undue experimentation.

Another embodiment of a stylet for use within an endoscopy needle isdescribed with reference to FIG. 4A, which shows asimplified/diagrammatic longitudinal section view of a fourth styletembodiment 400. The stylet 400 includes an elongate single-wire,memory-metal alloy body 402 with a generally cylindrical body profilethat is circumferentially bounded by a first outer circumference. Apolymeric distal tip member 406 is overmolded (or otherwisepermanently/fixedly attached) around a distalmost end length 404 of thesingle-wire body 402. The polymeric distal tip member 406 has agenerally cylindrical body profile like the single-wire body 402, and itis circumferentially bounded by a second outer circumference that isgreater than the first outer circumference. For example, in this andother embodiments the first outer circumference may be about one-half toabout 65% to about 95% of the second outer circumference.

Most of the distalmost end length 404 of the single-wire body 402 has athird outer circumference that is about the same as the first outercircumference (although it may be somewhat lesser or greater) and thatis less than the second outer circumference. The distalmost end length404 of the single-wire body 402 preferably occupies one-half or less ofthe longitudinal length of the polymeric distal tip member 406. As such,the unoccupied distal-most length of the polymeric distal tip member 406preferably will be even more flexible than the martensitic phasecontacting/immediately-adjacent length of the single-wire body 402,which will further provide for decreasing likelihood ofbinding/increased retraction force attributable to stylet stiffnessthrough certain lengths of a needle lumen (or other lumen) during use.

Another embodiment of a stylet for use within an endoscopy needle isdescribed with reference to FIG. 4B, which shows asimplified/diagrammatic longitudinal section view of a fifth styletembodiment 500. The stylet 500 includes an elongate single-wire,memory-metal alloy body 502 with a generally cylindrical body profilethat is circumferentially bounded by a first outer circumference along aproximal-most longitudinal length 502 a. A polymeric distal tip member506 is overmolded (or otherwise permanently/fixedly attached) around adistalmost end length 504 of the single-wire body 502. The polymericdistal tip member 506 has a generally cylindrical body profile like thesingle-wire body 502, and it is circumferentially bounded by a secondouter circumference that is greater than the first outer circumference.

Most of the distalmost end length 504 of the single-wire body 502(disposed within the polymeric distal tip member) has a third outercircumference that is less than the first outer circumference and thatis less than the second outer circumference. The outer circumference ofthe proximal-most longitudinal length 502 a tapers to a fourth outercircumference along an intermediate longitudinal length 502 b, which isless than the first outer circumference and which may be less than, thesame as, or greater than the third outer circumference. The proximallength 502 a including the first outer circumference will preferablyprovide desirable pushability and trackability along the proximal-mostabout 10% to about 70% of stylet body length, while the tapering lengthto the smaller fourth outer circumference preferably will provide asmooth transition that promotes responsiveness and is consistent withproviding enhanced flexibility and/or reduced likelihood of binding orretraction force required for at least a distal stylet length portion.This may be referred to as “stylet removal force.”

With prior devices, the stylet removal force can be quite high when aneedle or other device through which the stylet is disposed ispositioned through an endoscope contorted through a tortuous passage(e.g., as shown in FIG. 2). The natural/default disposition of thestylet wire is to straighten. Therefore when the stylet is being pulledaround/through the bends of the needle, the stylet is continuously“trying” to straighten. This means that the distal tip of the stylet iscontinuously being scraped against the wall of the needle, increasingthe interference and frictional force resisting retraction/removal. Ifthe tip of the stylet is more malleable (in martensite state) is willconform the to shape of the needle upon removal. This effect will beseen more in larger-gauge needles that contain correspondingly largerstylets. The same would apply for stylet embodiments with a polymerictip, where the polymeric tip will be constructed of a material that issofter/less stiff than the wire employed for the major body length ofthe polymer-tipped stylet embodiments.

The distalmost end length 504 of the single-wire body 502 is shown withenlarged portions 504 a that may help secure the polymeric distal tipmember 506 along with other fastening means (such as, for example,epoxy, adhesive, etc.) although, as above, the enlarged portion mayfunction alone to secure these elements together. The enlarged portion504 a is shown as having a barbed geometry, but those of skill in theart will appreciate that other shapes can be provided to assistinter-engagement of the distalmost end length 504 with the polymericdistal tip member 506. The distalmost end length 504 of the single-wirebody 502 preferably occupies one-half or less of the longitudinal lengthof the polymeric distal tip member 506. As such, the unoccupieddistal-most length of the polymeric distal tip member 506 preferablywill be even more flexible than the martensitic phasecontacting/immediately-adjacent length of the single-wire body 502,which will further provide for decreasing likelihood ofbinding/increased retraction force attributable to stylet stiffnessthrough certain lengths of a needle lumen (or other lumen) during use.

Yet another embodiment of a stylet for use within an endoscopy needle isdescribed with reference to FIG. 4C, which shows asimplified/diagrammatic longitudinal section view of a sixth styletembodiment 600. The stylet 600 includes an elongate single-wire,memory-metal alloy body 602 with a generally cylindrical body profilethat is circumferentially bounded by a first outer circumference. Apolymeric distal tip member 606 is fixedly attached directly at a distalend of the single-wire body 602. The polymeric distal tip member 606 hasa generally cylindrical body profile like the single-wire body 602, andit is circumferentially bounded by a second outer circumference that isgreater than the first outer circumference, while including ahemispherically-rounded or otherwise domed distal end terminus.

Each of the above embodiments may be useful in methods for accessing atarget site via a tortuous passage. For example, a tortuous passage mayinclude patient body passage and/or an endoscope, introducer sheath, orother passage where a more-flexible distalmost portion will beadvantageous for navigating a needle (with stylet in its lumen) andretracting the stylet with less force than required for a stylet havingconsistent flexibility along its entire length. The target site may bewithin a patient's body. The stylet may include memory metal materialand/or polymeric length(s) as described above, alone or in combinationwith each other.

Those of skill in the art will appreciate that embodiments not expresslyillustrated herein may be practiced within the scope of the claims,including that features described herein for different embodiments maybe combined with each other and/or with currently-known orfuture-developed technologies while remaining within the scope of theclaims. Although specific terms are employed herein, they are used in ageneric and descriptive sense only and not for purposes of limitationunless specifically defined by context, usage, or other explicitdesignation. It is therefore intended that the foregoing detaileddescription be regarded as illustrative rather than limiting. And, itshould be understood that the following claims, including allequivalents, are intended to define the spirit and scope of thisinvention. Furthermore, the advantages described above are notnecessarily the only advantages of the invention, and it is notnecessarily expected that all of the described advantages will beachieved equally with every embodiment. In the event of any inconsistentdisclosure or definition from the present application conflicting withany document incorporated by reference, the disclosure or definitionherein shall be deemed to prevail.

We claim:
 1. A stylet configured for use within an endoscopic needle,the stylet comprising: a proximal end terminus and a distal endterminus; an elongate single-wire, memory-metal alloy body with agenerally cylindrical body profile that is circumferentially bounded bya first outer circumference, extending distally from the proximal endterminus; a polymeric distal tip member fixedly attached directly at adistal end of the single-wire body; where the polymeric distal tipmember has a generally cylindrical body profile circumferentiallybounded by a second outer circumference that is substantially equal toor greater than the first outer circumference; and where at least alengthwise portion of the single-wire body is in martensitic phase atoperating temperatures at and below about 37° C.
 2. The stylet of claim1, where the polymeric distal tip member is overmolded upon and around adistal terminal-end length of the single-wire body.
 3. The stylet ofclaim 2, where the second outer circumference is substantially equal tothe first outer circumference, and the longitudinal distal terminal-endlength of the single-wire body that is within the polymeric distal tipmember comprises a third outer circumference that is less than the firstouter circumference and the second outer circumference.
 4. The stylet ofclaim 3, where the longitudinal length of the single-wire body that iswithin the polymeric distal tip member occupies about one-half or lessof the longitudinal distal terminal-end length of the polymeric distaltip member.
 5. The stylet of claim 3, where the third outercircumference is about 65% to about 95% of the second outercircumference.
 6. The stylet of claim 2, where the second outercircumference is greater than the first outer circumference.
 7. Thestylet of claim 2, where the first outer circumference is about 65% toabout 95% of the second outer circumference.
 8. The stylet of claim 2,where the longitudinal length of the single-wire body that is within thepolymeric distal tip member occupies about one-half or less of thelongitudinal length of the polymeric distal tip member.
 9. The stylet ofclaim 1, where the fixed attachment of the polymeric distal tip memberto the single-wire body comprises one or more of overmolding, adhesive,epoxy, friction-fit interface, or any combination thereof.
 10. Thestylet of claim 1, where the combined length of the polymeric distal tipmember and the lengthwise portion of the single-wire body in martensiticphase at operating temperatures at and below about 37° C. comprises atleast about one-tenth of the complete length of the stylet between itsproximal end terminus and distal end terminus.
 11. The stylet of claim1, where the combined length of the polymeric distal tip member and thelengthwise portion of the single-wire body in martensitic phase atoperating temperatures at and below about 37° C. comprises no more thanabout one-half of the complete length of the stylet between its proximalend terminus and distal end terminus.
 12. The stylet of claim 1, wherethe length of the polymeric distal tip member comprises at least aboutone-half of the complete length of the stylet between its proximal endterminus and distal end terminus, or no more than about one-half of thecomplete length of the stylet between its proximal end terminus anddistal end terminus.
 13. The stylet of claim 1, where the distalterminus of the polymeric distal tip member is hemispherical orotherwise rounded.
 14. A needle assembly including the stylet of claim1, further comprising an endoscopic needle, where the stylet is disposedthrough a longitudinal lumen of the needle.
 15. A stylet configured foruse within an endoscopic needle, the stylet comprising: a proximal endterminus and a distal end terminus; an elongate single-wire,memory-metal alloy body with a generally cylindrical body profile thatis circumferentially bounded by a first outer circumference, where theaustenite finish temperature (A_(f)) is greater than about 37° C.; andwhere at least a distalmost lengthwise portion of the single-wire bodyis in martensitic phase at operating temperatures below about 40° C. 16.The stylet of claim 15, where the austenite start temperature (A_(s)) isgreater than about 37° C.
 17. The stylet of claim 15, further comprisinga polymeric distal tip member fixedly attached directly at a distal endof the single-wire body; where the polymeric distal tip member has agenerally cylindrical body profile circumferentially bounded by a secondouter circumference that is substantially equal to or greater than thefirst outer circumference.
 18. The system of claim 17, where the firstouter circumference is about one-half to about 95% of the second outercircumference.
 19. The stylet of claim 15, where the length of thepolymeric distal tip member comprises at least about 5% of the completelength of the stylet between stylet proximal end terminus and distal endterminus.
 20. A method for accessing a target site via a tortuouspassage, the method comprising steps of: providing an access assemblyincluding a single-wire stylet disposed through a complete length of alongitudinal needle lumen of a needle, but not extending beyond a distalend terminus of the needle; where a distal-most length of the stylet hasabout the same outer circumference as, but a greater flexibility than, aproximal-most length of the single-wire stylet; where thegreater-flexibility length includes a polymeric distal tip member, amemory metal body length in martensitic phase at operating temperaturesat and below about 37° C.; directing a distal-most length of the needle,including the distal-most length of the stylet disposed through theneedle lumen, through a tortuous passage to a target site; andretracting the stylet at least proximally at least some distance withinthe needle lumen.